1. Field of the Invention
One or more embodiments of the invention relates to an organic light emitting diode device, and more particularly, to a tandem organic light emitting diode device.
2. Discussion of the Related Art
Recently, flat panel displays (FPDs) are becoming increasingly important with the development of multimedia. Accordingly, several planar display devices, such as a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), and an organic light emitting diode (OLED) device have been practical. In particular, the OLED device has a high-speed response of 1 ms or less, low power consumption, and self-light emitting characteristics. Also, the OLED device has a merit as a moving picture display media irrespective of the size of the display because it does not have a viewing angle problem. Further, the OLED device is being considered as the next generation flat panel display because it can be fabricated at a low temperature and is simply manufactured based on the existing semiconductor process technology.
The OLED device includes a light emitting layer between a first electrode and a second electrode. Here, a hole supplied from the first electrode is coupled with an electron received from the second electrode in the light emitting layer to form an exciton, and light is emitted by the energy generated while the exciton returns to the ground state.
The OLED device has been developed to have various structures, among which a tandem type white OLED device is becoming of interest. In the tandem OLED device, respective layers between the first electrode and the second electrode are deposited without masks, and the organic layers including light emitting layers are sequentially formed by depositing different compositions under vacuum conditions. In this white OLED device, white light is implemented by mixing colors of two or more light emitting layers. In this case, different light emitting layers that emit multiple color lights are provided between the first electrode and the second electrode, and stacks are differentiated based on a basic structure in which a charge generation layer is provided between each two adjacent light emitting layers.
However, the tandem white OLED device has problems in that the multiple light emitting layers respectively emitting different colors make it difficult to implement white light through the control of the light emitting efficiencies among the colors, and the light emitting efficiencies need to be improved.